When you accept that design happens almost everywhere in your organization, you have to take responsibility for it. Your app is slow? Go sit with your engineering team. Your marketing team is poorly communicating your product to future customers? You’d better offer to work with them on the problem.
Yes, doing design with everyone at your company is a lot of work. But it’s necessary if you want to be a truly great designer — otherwise, you’re simply papering over bad decisions. For example, imagine that your CEO created a complex pricing structure for your product. You could focus on making the pricing page as clear as possible using your interface and information design skills. But the harder and more important design opportunity is to work with your CEO on repricing your product so it’s clear to customers and compatible with the business goals.
Focusing on the core business is what differentiates real product design from interface design or even user experience design. Fundamental product design is really hard and requires a lot of legwork, but this is what designers at the highest level do.